1. Field of the Invention
The subject invention relates to a process for preparing s-triazine radical containing polyether polyols. More particularly, the subject invention relates to a process for preparing such polyether polyols by oxyalkylating one or more polyamino-1,3,5-triazines and optionally an alkanol, water, or both alkanol and water, in the absence of both catalysts and inert polar solvents. The polyether polyols are especially suited for the preparation of rigid polyurethane, polyisocyanurate, and urethane group-containing polyisocyanurate foams.
2. Description of the Related Art
The preparation of oxyalkylated polyamino-1,3,5-triazines is described in Federal Republic of Germany OS 21 18 868 (U.S. Pat. No. 3,812,122). In this process, polyamino-1,3,5-triazines are oxyalkylated with alkylene oxides in the presence of basic catalysts in N,N-dialkylcarboxamide solvents at temperatures of from 90.degree. C. to 200.degree. C.
Polyhydroxyalkylamino-s-triazines may be prepared in accordance with U.S. Pat. No. 3,328,321 by reacting amino-s-triazines such as melamine with ethylene carbonate or alkylene oxides in the presence of basic catalysts and solvents such as diethylene glycol dimethyl ether and dimethylformamide. These polyhydroxyalkylamino-s-triazines have hydroxyl numbers of from 150 to 450 and may be used alone, or mixed with conventionally used higher molecular weight compounds containing reactive hydrogen atoms, such as polyether polyols, polyester polyols, and polyamides, in the preparation of cellular polyurethanes.
Oxyalkylated polyamino-1,3,5-triazines may be prepared in accordance with U.S. Pat. No. 3,438,986 wherein oxyalkylated aryl diamines are used as solvents. The resulting mixtures of oxyalkylated aryl diamines, oxyalkylated triazines, and oxyalkylated organic hydroxyl compounds are also suitable for preparing polyurethane foams.
As described in British Pat. No. 1,064,148, mixture of amino-1,3,5-triazines and aliphatic or aromatic, saturated or unsaturated polyols may be oxyalkylated in the presence of basic catalysts at temperatures of from 75.degree. C. to 175.degree. C. As described in the specification, the use of inert solvents can sometimes be eliminated in the oxyalkylation process. However, when melamine and other aminotriazines having low-solubility and relatively high melting points are used as one of the co-initiators, it is recommended that dimethylsulfoxide solvent also be used.
The foregoing procedures have a disadvantage in that the oxyalkylation of the polyamino-1,3,5-triazines must always be performed in the presence of basic catalysts, for example alkali metal hydroxides or alkoxides, and that oxyalkylated aryldiamines or inert polar solvents such as dimethylformamide or dimethylsulfoxide must be used. Since the process expenses for separating both the high-boiling-point polar solvents and the catalysts are considerable, the oxyalkylated aminotriazine-containing polyether polyol product mixtures so far have not established themselves commercially as basic components for preparing polyurethanes.